Extract Horizontal Slices from Voxel

Use the Voxel > Utilities > Extract Horizontal Slices from Voxel menu option (geogxnet.dll(Geosoft.GX.VoxUtils.VoxelHorizontalSlice;Run)*), to extract horizontal (plan) grids from a voxel model.

The option can also be found on the Add to 3D > Grids menu in the 3D Viewer.

Extract Horizontal Slices from Voxel dialog options

Input voxel

Select the voxel file from which to extract slice(s).

If the file selected is a vector voxel, the generated output will be an amplitude grid.

Script Parameter: VOXHORIZONTALSLICE.VOXEL

Output file base name

Provide a prefix for the output grid(s). The output grid names are constructed using the Output file base name as a prefix followed by Start elevation/ Start offset. For instance, if the file base name is "plan", then the actual grid created at 500 m below the starting datum would be plan_-500.grd.

Script Parameter: VOXHORIZONTALSLICE.GRID

Constant elevation | Reference surface grid

Surfaces can be created either as horizontal slices at constant vertical elevations (Default), or as slices parallel to a user specified elevation.

Script Parameter: VOXHORIZONTALSLICE.SURFACE_TYPE [0: Constant elevation, 1: Reference surface grid]

Reference surface

This field is only enabled when the Reference surface grid option has been selected. When enabled, this is a required field. Select an elevation grid that overlaps with the voxel and resides in the same projection system. The coverage of the extracted grids will consist of the area covered by both the grid and the voxel. No data is extracted from the voxel where the elevation grid has no values.

Script Parameter: VOXHORIZONTALSLICE.REFERENCE_SURFACE_GRID

Start elevation | Start offset

This is a contextual entry:

  • If Constant elevation has been selected above, the Start elevation is in the georeferenced coordinate system and indicates the datum of the first surface.

  • If Reference surface grid has been selected above, the Start offset indicates the vertical offset from the provided surface grid. The offset assumes Z-axis up. If no elevation is specified, then elevations will be selected based on the top of the voxel or the elevation grid.

Script Parameter: VOXHORIZONTALSLICE.START_ELEV

Elevation increment | Offset Increment

Specify the increment in elevation when more than one grid is requested. If no elevation increment is specified, then a single grid is extracted.(See below for a full description).

Script Parameter: VOXHORIZONTALSLICE.ELEV_INC

Number of grids

Specify the number of grids to extract. If not specified, then a single grid is created at the input start elevation. (See below for a full description).

Script Parameter: VOXHORIZONTALSLICE.NGRIDS

Output cell size

Select the cell size of the output grid(s). If left blank, the cell size will be set to the voxel horizontal cell size.

Script Parameter: VOXHORIZONTALSLICE.CELLSIZE

Interpolation method

Select one of the options below: 

Linear: interpolates a value from the voxel values closest to the grid cell centre locations.

Nearest:  finds the closest location in the voxel model and uses it.

Script Parameter: VOXHORIZONTALSLICE.INTERP [L: Linear, N: Nearest]

Display

This entry is only enabled when running the tool from the 3D menu. If this GX is launched from within the 3D viewer, then the grids are automatically displayed inside the viewer.

If this GX is launched from the 3D menu, select how to display the created grids. Select one of the options below:

Current map: Not available if there is no current map; automatically selected otherwise. If the current map contains a 3D view, then the grids will be displayed into the 3D view of the current map. If the current map contains a 2D view, then the grids will be displayed in 2D.

Display in grid windows: All grids are opened in individual 2D views.

Do not display: If selected, the grids will be added to the project, but not displayed.

Script Parameter: VOXHORIZONTALSLICE.DISPLAY [C: Current map; D: Display in grid windows; X: Do not display]

Colours

Select the colour scheme for rendering the image of the selected grid. If you mouse over the colour scheme entry, a tooltip will display the name of the colour table in its folder. To modify the selection, click on the colour entry and then navigate through the scheme categories.

Script Parameter: VOXHORIZONTALSLICE.COLOUR_TABLE

Colour method

Select a colour method. This selection is ignored if a colour file is defined as a zone (.ZON) or a transform (.ITR) file.

As last displayed: If the same grid has previously been created, its previous colour transform is used, and takes precedence.

Default: Use an equal-area histogram transform if no transform is present.

Histogram equalization: Data is binned and approximately the same number of items are assigned to each colour.

Normal distribution: A normal distribution is applied, based on the standard deviation and mean calculated from the voxel statistics.

Linear: The minimum and maximum voxel values define the endpoints.

Log-Linear: A logarithmic distribution, with adjustments for negative values.

Script Parameter: VOXHORIZONTALSLICE.COLOUR_METHOD [0: Default; 1: Linear, 2: Normal distribution, 3: Histogram equalization, 5: Log-Linear, 6: As last displayed]

Application Notes

*The GX tool will search in the "...\Geosoft\Desktop Applications \gx" folder. The GX.Net tools, however, are embedded in the geogxnet.dll located in the "...\Geosoft\Desktop Applications \bin" folder. If running this GX interactively, bypassing the menu, first change the folder to point to the "bin" folder, then supply the GX.Net tool in the specified format.

Extract Plan Grids from a Voxel Model

The output grids are automatically trimmed to eliminate locations beyond the edges of the voxel model, and are given an orientation warp so they may be readily plotted in a 3D view. If a selected elevation does not intercept any data, then no grid is produced at that elevation, and a warning message is displayed.

Specify Elevation, Elevation Increment, and Number of Grids

This method allows a wide variety of output grid slicing methods, based on which of the elevation, elevation increment and number of grids parameters are specified. You may specify one, two or three of these parameters.

The voxel model is scanned to determine the actual range of elevations that contain valid data.

The resulting behaviour is described in the table below:

Start Elevation

Elevation Increment

Number of grids

Behaviour

Z0

DZ

Undefined

A single grid at Z0.

Z0

Undefined

N

If Z0 is below the voxel, then the voxel is divided into N layers, and the slices are taken at the centers of the slices (and the starting elevation is ignored).

If Z0 inside the valid range of elevations, the first grid is at Z0, and the remainder are positioned by dividing up the elevations above the start elevation into N-1 slices, and using the center elevations of the slices.

Undefined

DZ

N

The elevations are centered on the voxel vertical data bounds.

Z0

Undefined

Undefined

A single grid at Z0.

Undefined

DZ

Undefined

Grids are produced at integer multiples of DZ for the entire vertical range of data in the voxel.

Undefined

Undefined

N

The vertical range of data is divided into N equal slices, and the centers of the slices define the grid elevations.

Undefined

Undefined

Undefined

A single grid at the center elevation of the available data.

Defined

Defined

Defined

Only those grids with valid data are produced.